Re: [pph] Adapting LTO streaming for front end AST saving

[Richard Guenther <rguenther@suse.de>]

On Wed, 23 Mar 2011, Diego Novillo wrote:

> Over at the PPH branch we are starting to re-use the LTO streaming
> routines to save front end trees.  Clearly, there are things that need
> to be extended and/or replaced since LTO streaming assumes that we are
> in GIMPLE.  However, there is a large intersection that I think can be
> commoned out.
> 
> - ASTs do not need to concern themselves with language differences.
> They are generated and consumed by cc1plus, so saving
> language-dependent information is fine.
> - LTO streaming has several checks and assumptions that prevent
> non-gimple trees (e.g., DECL_SAVED_TREE must be NULL).
> 
> I'm looking for opinions on what would be the best approach to factor
> out the common code.  So far, I have created a layer of routines and
> data structures that the front end calls to manipulate PPH files.
> These are wrappers on top of LTO streaming that deal with all the
> sections, buffers and streams used by LTO.
> 
> I was thinking of using langhooks to do things like checks (like the
> check for DECL_SAVED_TREE in
> lto_output_ts_decl_non_common_tree_pointers or the asserts in
> lto_get_common_nodes).  I'm expecting that there will be other things,
> like handling more tree nodes in the tree streaming routines.  But
> everything else seems to be already sufficiently flexible for our
> needs.
> 
> Thoughts?

Yes, Micha has a load of patches cleaning up streaming and removing
unecessary abstraction.  So, why'd you need to share any of it?  I
think it would be much easier if you worked with a copy (ugh,
streaming trees again....).

Richard.